ACTRN12607000321448.

Methods	Randomised placebo controlled trial.
Participants	Location: Australia. Single centre. Setting of recruitment and treatment: WA Centre for Health & Ageing, University of Western Australia. Inclusion criteria: Adults with mild cognitive impairment (‐1.5 standard deviations below norm on any task in the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) neuropsychological battery); Over 65 years of age; Vitamin D concentration between 12.5 and 50 nmol/L at baseline. Exclusion criteria: · Diagnosis of osteoporosis requiring treatment; · No informant available; · Severe physical or medical illness that would preclude completion of the trial; · Hearing or visual impairment that would preclude assessments; Already in an intervention trial; · Clinical history of stroke; · Fall in the last 3 months; · Heart attack in the last 3 months; · Fall with fracture over the age of 65 years; · History of kidney or bladder stones; · Current acute depression; · History of schizophrenia; · Current diagnosis of dementia.
Interventions	Intervention : 1000 IU vitamin D daily by oral tablet. Comparator group: Placebo (soyabean oil tablet indistinguishable from active tablet).
Outcomes	Outcomes of interest in the review: Overall cognitive functioning: Cambridge Examination for Mental Disorders in the Elderly ‐ Cognitive section (CAMCOG); Specific cognitive functioning subdomain: executive function: digit‐symbol coding task; Specific cognitive functioning subdomain: episodic memory: California Verbal Learning Scale‐Revised; Development of dementia; Quality of life: SF‐12.
Reason awaiting classification	Only publication of baseline results and protocol found. No results available after contact with authors.
Notes	National Health and Medical Research Council Dementia Research Grants Program